Software Engineering for Students A Programming Approach

following list of requirements:
■ an adequate set of primitives for defining procedural abstractions
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■ safe and efficient mechanisms for controlling communication between program units
■ simple, clearly defined mechanisms for controlling access to data objects defined
within program units.
Procedures and functions
The basic procedural abstraction primitives provided in programming languages are
procedures and functions. Procedures can be thought of as extending the statements of
the language, while functions can be thought of as extending the operators of the language.
A procedure call looks like a distinct statement, whereas a function call appears
as or within an expression.
The power of procedural abstraction is that it allows the programmer to consider the
method as an independent entity performing a well-described task largely independent
of the rest of the program. When a procedure is called, it achieves its effect by modifying
the data in the program which called it. Ideally, this effect is communicated to the
calling program unit in a controlled fashion by the modification of the parameters
passed to the procedure. Functions, like their mathematical counterparts, return only
a single value and must therefore be embedded within expressions. A typical syntax for
writing procedures and functions is shown below:
void procedureName(parameters) {
declarations
procedure body
}
resultType functionName(parameters) {
declarations
function body
return value;
}
It is critical that the interface between program units be small and well defined if we
are to achieve independence between units. Ideally both procedures and functions
should only accept but not return information through their parameters. A single result
should be returned as the result of calling a function.
For example, to place text in a text box, use a procedure call as illustrated by the following
code:
setText("your message here");
and a function call to obtain a value:
String text = getText();
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